Bacteria in the peritoneal cavity gain access to circulating blood via trans diaphragmatic absorption into lymp vessels. Specific information is lacking but it is generally assumed that this protects the host by "clearing" bacteria from the peritoneal cavity. The results of preliminary studies carried out in our laboratory suggest that this assumption is incorrect. Thus survival of rats with early fecal peritonitis was significantly enhanced by the intraperitoneal (IP) administration of platelets, a maneuver known to block transdiaphragmatic absorption of bacteria size particles. This finding requires further study and the next logical steps, which form the basis for this proposal are to determine the specific effectiveness of IP platelets in excluding IP injected E. coli and bacteroides from lymph and blood: and to examine the effect of repeated IP injections of platelets on the survival of rats with advanced fecal peritonitis.